A bit rough but someone has loved it!

[GRC]

Hi Mark.

I assumed your use of "sulphate" was accidental  Just wanted to clear it up for other members. 

 

As for solubility,

2 hours ago, mas4t0 said:

While the solubility is low enough to classify Ag2S as insoluble, it is not truly 100% insoluble (in the binary sense). This is also of course assuming pure water.

I completely agree, and wasn't disputing that at all.

 

As for weight vs mass, 

Once again, I completely agree that they are different terms with different meanings.

"Mass", as you say, is certainly the correct term to use.
I chose to use the word "weight" because that was the word most people were using in their posts, and what they would typically use when speaking to other people, so at the time, I didn't think it was necessary to add another layer of nuance to the scientific terminology being used.

In hindsight, I probably should have included "mass" in my statements.

Again, this illustrates the omnipresent issues with discussing scientific or technical concepts in a chat or forum-post type of format. 

    

Ultimately, my goal in posting was to try to bridge the gap between academic science and a "layman's" understanding, where perhaps the last bit of science training someone had was back when they were in high school  

 

 

Dirk,

thanks for posting the closeup pic 

The spread and rise of the tarnished silver are both clear in that photo. 

[rkg]

I've been fascinated with the dendritic growth you sometimes see from silver on tsuba - still don't understand the mechanism (is there something on the surface that enables this, etc):

 

 

 

 

Best,

rkg

(Richard George)

 

[vajo]

George i don't belive in growing silver. I think that is from fire guilding. Sometimes you see silver and gold particles all over the surface. But what i know...

[ROKUJURO]

Glen and Mark,

 

thank you for correcting my clumsy text! Yes, I should have used 'metal object' and 'mass' insted of element and weight!

Sometimes, I simply write too fast and miss the correct expressions!  

 

[rkg]

On 7/17/2022 at 11:48 AM, vajo said:

George i don't belive in growing silver. I think that is from fire guilding. Sometimes you see silver and gold particles all over the surface. But what i know...

Chris,

Oh, its "growth" alright. it wipes right off if you're not "careful".  several of the images above came off of this piece - you can see the "blooms" on the silver in this image:

 

 

You usually see this kind of metal migration in the presence of an electric field (used have to plan to defeat this when doing PC board designs (no joy to have one grow between the power and ground traces on your 48v supply, but I digress).

 

And...  you see this happen a LOT to silver nunome on older pieces - which isn't fire guilded.

 

Best,

rkg

(Richard George)

[GRC]

Richard, you peaked my curiosity...

Love that tsuba too btw 

 

Interestingly, I found a scholarly article on the dendritic growth of silver, and it happens in the presence of sulfate ions (S04 with a 2- charge)... that's a sulfur atom combined with 4 oxygen atoms, which will interact with the silver ions in such a way as to allow for the silver to travel/grow in a dendritic pattern (similar to the branches of a tree, or branching neurons in the brain, or "fractal" patterns in general).

 

So here is one possible explanation for what we're seeing on that tsuba:

Some of the captured sulfur in the silver tarnish would have to have reacted with some source of oxygen to become sulfate ions. (not too sure how readily this occurs in the environment of a tsuba's surface during feudal Japan , but let's assume it happens)

Then throw in the presence of some moisture for the silver and sulfate ions to interact in solution, then voila, you will get dendritic growth of silver.  

(remember that there are some silver and sulfur ions present in the tarnish, which will dissolve in water, even though the tarnish is mostly a covalently bonded network solid that will mostly not dissolve in water)

 

The image below shows lumpy/clumpy growth of silver in the presence of nitrates (nitrogen with 3 oxygens), but dendritic growth in the presence of low concentrations of sulfates (sulfur and 4 oxygens).  

This growth occurred on a sheet of copper in this experiment, but I imagine it would be similar on some other metal (like an iron tsuba).

 

Here's the link to the article if anyone else is interested:

Fast Growth Synthesis of Silver Dendrite Crystals Assisted by Sulfate Ion and Its Application for Surface-Enhanced Raman Scattering | The Journal of Physical Chemistry C (acs.org)

 

Video of the dendritic growth (looks like a whole coral reef is growing, but it's silver):

https://doi.org/10.1021/jp201484r